text: Vflo considers the spatial character of the parameters and precipitation controlling hydrologic processes, and thus improves upon lumped representations previously used in hydrologic modeling.  Historical practice has been to use lumped representations because of computational limitations or because sufficient data was not available to populate a distributed model database.  Advances in computational speed; development of high-resolution precipitation data from radar and satellites; and availability of worldwide digital data sets and GIS technology makes distributed, physics-based modeling possible.  Vflo is designed to take advantage of the spatial variability of high resolution radar rainfall input, GIS datasets, and hydraulic channel characteristics.  Because it is physics-based, it produces hydrographs based on conservation equations and the hydraulics of the drainage network, and can be employed in locations where there are no rain gauges or previous modeling studies.  In addition, Vflo’s network approach makes models scalable from upland watersheds to river basins using the same drainage network.